It may be necessary, for various reasons, such as, for example regulation of breaks, shift planning, faults or cycles in the production process, to temporarily move entire production plants or parts of production plants to a standby state for the purpose of saving energy.
In this case: “standby” refers to a device state, in which at least one function, but not the main function, is fulfilled, in which a significantly reduced energy consumption prevails and the main function can be activated again at any time without preconditions. However, activating and leaving standby states (“switching process”) is not instantaneous, that is to say immediate, but instead requires a certain amount of time.
Depending on the degree to which the energy consumption is reduced, several different “depths” of standby state may furthermore exist, which result from the individual nature of the respectively observed plant or sub-plant or components.
On account of the complex design of production plants and the processes executed, the system composed of production plant and functions is dynamic, whereby the temporary movement of entire plants or parts thereof to a standby state requires precise knowledge about properties and relationships of the entities involved on different observation levels (component, unit, sub-plant, etc., in context with process step, sub-process, etc.) with respective dependencies.
Essential variables are the times for reaching standby from the main function and reaching the main function from standby as well as the minimum and maximum dwell time in standby.
Further variables may be plant-structure-specific or process-specific preconditions, which may have priority over the pure time observation. Furthermore, during the switching process, so-called “synchronization states” may be relevant, in which, first of all, dependent entities must have occupied specific states and which must be identified and characterized separately.
Switching processes and their consequences have to be able to be tracked and monitored. Switching processes in plants therefore have to follow specific sequences of switching actions, subsequently also referred to as switching paths, which result on account of features of the entities and the knowledge about the nature of the plant. However, this is subject to changes (for example due to retrofitting) in accordance with the lifecycle thereof, with effects on the validity of the switching paths, which then have to be adjusted. Individual components along the paths are then controlled for moving to a standby state or for reactivation by corresponding technical means, for example by means of PROFlenergy commands.
A prerequisite for the determination and processing of switching paths is a sufficiently complete plant model, which describes the design of a production plant under the following aspects:    hierarchy,    units and individual components and their relationships to one another with respect to production cycles, technical boundary conditions etc.,    state machines, the design of which results from the possible standby states of the entities with respective energy saving, the respectively required switching times and possibly present restrictions of the switching options of the components; these are dependent on the respective components themselves and on their individual interconnections.
Until now, the required “plant switching model” has thus been formed and provided with the further required information manually in a separate engineering step. Although the knowledge about the underlying relationships is then found in the model again, said knowledge is used only manually for determining the restrictions that are to be assumed. The possible switching paths are then determined from said predefined features and characteristic variables and transmitted to a downstream software component for controlling and monitoring the switching processes.
Connections to the plant communication system that are to be parameterized likewise serve for monitoring and controlling the progression along the switching paths.
If there are changes to the plant, the separate plant switching model has to be traced using the relevant information and the switching paths have to be regenerated and implemented manually. This energy-efficiency-related work constitutes additional outlay in the device and in the operation of plants, in terms of both data storage and the working steps.
Nowadays, the necessary information is available in various engineering tools, documents and possibly as knowledge of individuals involved (plant drivers, operators, commissioning engineers) and has to be evaluated manually.
In the following text, known types of dependencies in switching processes for the purpose of changing the energy requirement of an automated machine or plant and the underlying causes are described.
In the following text, “dependency” means that for a specific switching process conditions have to be fulfilled in order for the switching process not to lead to a fault state of the plant or individual components.
1. There are dependencies regarding the ability to reach communication partners: other components must be able to be reached (for example for registering or confirming the ability to reach a “neighboring station”, etc.).    Exceptions to this would be    Safety: for an automatic mode, generally all participants in a safety circuit must be able to be reached in order that said safety circuit can be closed.    Mutual registration: plants can be implemented in such a way that a start-up process always leads to a fault (mutual request of both communication partners in the case of not absolutely synchronous start-up). In such a case, automatic acknowledgement of faults may be necessary as a “switching action”.
2. There are dependencies on the media supply, ancillary units and/or infrastructure components: plants and/or components can generally only be operated in an expedient manner when the supply with various media is guaranteed to a certain extent. (Cooling water, technical gases, compressed air, etc.). The operation of plants may require secondary processes or infrastructure elements to be present in specific states (for example industrial extractor, room air conditioning systems and lighting are switched on).
3. There are dependencies in the material flow: coupled plants may require upstream or downstream plant parts to be switched on, in particular when the two plant parts are involved in transfer processes. Switching strategies may possibly be derived at the same time from material flow dependencies. In an extreme case, only plant parts through which a part is currently running are always switched on.
4. There are start-up processes: it may be necessary during switch-on to observe chronological orders and possibly temporal boundary conditions when processes require this, such as warming phases, start-up of machine tools, decoupling of switch-on peaks.
5. There are shutdown processes/cycle ends
In this case, there may be process engineering reasons for switch-off chronological orders and follow-up times (for example cooling phases). Working steps are not able to be interrupted arbitrarily, but instead must first be brought to a defined end state (for example a safe state of a machine or plant) (also referred to as “cycle end”).
Representatives of the problem solution described above are found, for example, in the Siemens-internal activities such as the prototype implementation of a so-called “energy state controller”, which is already known from EP 2726945 A1.
Other patent applications in the context of energy-related switching systems are known, for example:                a system for automatically creating switching sequences taking into account energy-related threshold values (EP 2798418 A1)        the initial determination of system parameters by means of automatic iteration of synthetic operating scenarios (EP 2729845 DE)        a configuration tool for energy behavior of plant components (EP 2729853 A1)        a switch-off and restart-up concept for plants for increasing energy efficiency, based on autonomous systems (EP 2802947 A1),and in the context of sequence generation:        dynamic task flows and generation thereof (WO 2009/021540).        